1. Field of the Invention
Implementations of various technologies described herein generally relate to methods and systems for processing seismic data.
2. Description of the Related Art
The following descriptions and examples are not admitted to be prior art by virtue of their inclusion within this section.
Seismic data signals are typically acquired by measuring and recording data during a seismic survey. A seismic survey may be performed by repeatedly firing an impulsive seismic energy source at the surface of the earth, sea or seafloor and recording the received signals at a set of sensors. The sensors may typically be situated at the same surface as the source, but laterally displaced on regular grid positions. However, there may be situations where a non-regular distribution of the sensors is preferred or where the source and the sensors may be positioned at different depth levels. In a typical seismic survey, the source and the sensors may be displaced at fixed intervals (e.g., 25 meters) and in a certain direction (e.g., the “inline” direction).
During the seismic survey, the cycle of firing the source and recording the received signals may be repeated a plurality of times. When firing the seismic source, a pressure wave may be excited and propagated into the subsurface. The pressure wave reflects off interfaces between various earth layers (such as rock, sand, shale, and chalk layers) and propagates upwardly to the set of sensors, where the particle velocity of the wave vibrations or the pressure oscillations of the wave may be measured and recorded.
However, acquiring low-frequency seismic data may be difficult. One approach involves using vibroseis sources that are configured to emit a source spectrum that is richer in lower frequencies than typical seismic sources. However, the low-frequency output from vibroseis sources is limited by the size of the vibroseis, and its sweep time.